This invention relates generally to electrical switches and more particularly to relay switches which must be closed mechanically and which may be opened both mechanically and electrically.
It is often desirable in the case of home appliances such as washers and dryers, dishwashers, and other appliances, to provide a main power switch which can be manually closed by the user to initiate appliance operation and which can be opened automatically at the end of the operating cycle and which may be quickly manually opened by the user, when desired, such as in the event of a malfunction situation or a need to abort the operating cycle. In appliances incorporating an electromechanical timer the timer is arranged to mechanically open a power switch at the end of the cycle. In addition, the user can manually turn the appliance ON and OFF by manipulating the timer control knob. However, in an electronically controlled appliance, the electromechanical timer is replaced by an electronic controller which does not employ a timer control knob. Thus, a switch separate from the electronic controller is needed to provide the desired mechanical ON and both a mechanical OFF and an electrical OFF power control capability for electronically controlled appliances.
It is additionally desirable for home appliances with electronic controllers that momentary interruptions in power not cause the ON/OFF switch to switch OFF. Typically, the memory devices of such electronic controllers are capable of retaining information for a matter of seconds. Thus, a momentary power interruption will not adversely affect appliance operation provided the ON/OFF switch remains on.
One type of Push-to-Start switch which can be employed in electronically controlled washers and dryers is of the type illustrated in U.S. Pat. No. 3,622,925 in which a manually operable switch after mechanical closure is magnetically maintained in closed position by electromagnetic means. In such a switch, opening of the switch at the end of the cycle is accomplished by de-energizing the electromagnetic means. Such a switch provides the mechanical ON and electrical OFF operating mode but not a mechanical OFF mode. A further disadvantage of such a switch is that in the event of even a momentary interruption of power the electromagnetic means is de-energized and the switch opens. Once opened, the switch remains open until subsequently manually closed by the operator.
It is therefore an object of this invention to provide an ON/OFF relay switch assembly which provides a manually operable mechanical ON and both a manually operable mechanical OFF and an automatic electrical OFF and which does not switch OFF in response to power interruptions.
It is a further object of this invention to provide an ON/OFF relay switch assembly of the above type which is reliable and which is structurally relatively simple and inexpensive to manufacture.